I have a book called "Tweedlioop" by Stanley Schmidt. I have the same ISBN as another book in the system, but the book on PBS is a hard cover with a different picture and publisher. How do I add my own book, with accurate cover, size, and publisher info?

You cannot change the binding type for an existing listing, so if you have a paperback while PBS has a hardcover, you'll need to use the Post a Book Without an ISBN feature. It's on the Post Books page.

If your book actually is a hardcover, then you don't need to worry about the cover image or publisher. You only have to match the author, title, ISBN and binding type.

You can do this by posting a book "without an ISBN" from the Post Books page (righthand link on the yellow bar on that page). First make sure that your book is not an ARC (Advanced Reader Copy), as those aren't swappable on PBS. When you post the book without an ISBN, you will be able to add all of the information for the copy that you have (binding, publisher, upload a cover image, etc).